Linker error?

It keeps giving me a Linker error in the DaysOut function and also the findAverage function. I have no idea what is wrong and I've been trying to throw in all sorts of different combinations but I just can't seem to get it compiled. Any help is appreciated

Technically this means you are declaring 2 different versions of each function. In your main() you are calling the versions that you forward declared (daysOut(), no parameters) which has been declared but never defined.